This invention relates to a process for the production of silicic acrylate compounds and their resinous products by chemically reacting a silicic acid compound with an acrylic compound to produce a silicic acrylate compound. The silicic acrylate compound may then be polymerized with a catalyst such as a peroxide initiator.
The silicic acid compound used in this process may be produced by the chemical reaction of a dry alkali metal metasilicate with a mineral acid or an acid hydrogen containing salt. The silicic compound produced by this method was analyzed and contained hydrogen, oxygen and silicon in the ratio of about 2 mols of hydrogen to about 2 mols of oxygen to 1 mol silicon. The silicic acid used on the following examples was produced by reacting dry granular alkali metal metasilicate with an hydrogen containing acid salt or a concentrated mineral acid. The white granular silicic acid is washed with water, filtered and then air dried at 25.degree. to 75.degree. C. The white granular silicic acid was analyzed by infrared analysis, using the 1R KBr disc method. The infrared analysis was very similar to that obtained with Mallinckrodt's hydrated silica except for the area which shows the presence of Si--H bonds. The Mallinckrodt's hydrated silica (SiO.sub.2 .sup.. .sub.x H.sub.2 O) has a molecular weight of 60.09 .sup.. .sub.x H.sub.2 O. The said silicic acid contains an active hydrogen which will reduce silver nitrate in an aqueous solution which is evident that Si--H bonds are present.
When the said silicic acid is heated to much above 105.degree. C, silicon dioxide with a molecular weight of about 60 is produced. On further heating, it has a melting point of 1650.degree. C. In cryoscopic and ebullioscopic determination, the silicic acid produced was not soluble in any common organic solvent but was readily soluble in dilute alkali metal hydroxide aqueous solutions.
The molecular weight was determined from the boiling point elevation of said silicic acid in a 6N sodium hydroxide solution and indicated a molecular weight of 78 .+-. 25gm/mol. This type of reactive solution normally changes the molecular species. However, this would seem to indicate the absence of a polymeric form of silicate. This analysis may indicate a possible formula of H Si(OH).sub.3 (orthosilicoformic acid) and the presence of some metasilicic acid (H.sub.2 SiO.sub.3) while in solution. The orthosilicoformic acid when dried will lose water to form silicoformic acid (H.SiO.OH).
To produce the silicic acid compound used in this process, it is necessary to use a dry alkali metasilicate instead of using an aqueous solution of an alkali metasilicate to avoid producing silicic acid gel, silica and/or silicon dioxide. I have performed experiments reacting an aqueous solution of sodium metasilicate with an acid to produce silicic acid gel, silica and silicon dioxide, then by using the same procedure as used in my examples, I have been unable to react chemically dry granular silicic acid gel, silica or silicon dioxide with an acrylic compound. The silicic compound produced by my process reacts chemically with the acrylic compound, and when polymerized it produces a poly(silicic acrylate) polymer; the silicic acid compound produced in my process does not precipitate out and is soluble in many solvents.
The exact course of the reactions which take place during the process to produce poly(silicic acrylate) polymers cannot be determined with 100% certainty.
The silicic acrylate compounds may be co-polymerized with other polymerable compounds such as methyl methacrylte, styrene, allylchloride, acrylonitrile, vinyl chloride, butadiene and other polymerizable compounds.
The silicic acrylate resinous products produced in my process may be ground into a powder, softened with heat and then molded into useful products. The silicic acrylate resinous products are soluble in common solvents such as aqueous ammonium solution, acetic acid, alcohols, dilute sulfuric acid, alkali metal hydroxide solutions, acetone and other organic solvents. A solution of the silicic acrylate resinous products may be painted on wood and used as an adhesive or a tough protective coating. The silicic acrylate resinous products will form dispersions in aqueous solutions and may be painted on wood and forms a tough protective coating when dried.